1. Field
One embodiment of the present invention relates to a method and apparatus for manufacturing a patterned media, and more particularly to a method and apparatus for manufacturing a discrete track type patterned media having a center hole.
2. Description of the Related Art
A patterned media in which a magnetic layer is processed in patterns of servo signals and tracks or data bits has been studied as a high density magnetic recording media. Methods for manufacturing a patterned media are roughly classified into two types: a method in which a magnetic layer deposited on a substrate using a conventional method is etched by reactive ion etching (RIE), ion milling and the like; and a method in which a substrate is etched in advance and then a magnetic layer is deposited on the substrate using a conventional method. In any of these methods, dust or local mechanical degradation of a recording media becomes a problem because of the additional patterning process of the magnetic layer.
In particular, this problem is serious in the inner peripheral portion of a disk media. When a resist is spin-coated on the disk for patterning, the resist is likely to flow over the inner peripheral portion of the disk. In addition, the concentration of an electric field at the inner peripheral portion of the disk in RIE or ion milling process causes non-uniform or etching dust. Thus, the inner peripheral portion of a disk substrate is a location where the above problem is likely to occur. This location is hard to be cleaned. In spin-washing process, where a washing liquid is sprayed on the spinning substrate, sufficient cleaning effect is hardly obtained because a linear velocity is low at the inner peripheral portion. In addition, accumulated chemicals at the inner peripheral edge become a source for additional dust or defects of a media. In the case of a so-called dry process such as plasma irradiation, complete cleaning cannot be achieved because of non-uniformity in electric field as described above. In a semiconductor process, since typical substrate is a flat plate without a center hole, above mentioned problems at the inner peripheral portion do not occur in principle. Therefore, these problems are specific to a disk substrate. The semiconductor process has a long history, and a variety of techniques have been developed. However, such technical knowledge is not so helpful to the problems due to the center hole.
Jpn. Pat. Appln. KOKAI Publication No. 2004-79992 discloses a semiconductor manufacturing process in which contaminating particles are removed by a cryogenic cleaning process using CO2 after chemical mechanical polishing (CMP) of a semiconductor material. In this method, liquid CO2 is sprayed through a specially designed nozzle, for example, under a pressure of 850 psi (5.8 MPa) at 25° C. Since the liquid CO2 is sprayed into an atmospheric pressure, it is rapidly expanded and cooled down. This results in the mixture of gas, liquid and solid CO2. The flow of the gaseous and solid CO2 is directed to the wafer surface using the nozzle. Cryogenic particles that reach the wafer surface at a high speed and collide with contaminating particles can overcome adhesion of the contaminating particles to the wafer surface through transfer of momentum, and can remove the contaminating particles directly. However, the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-79992 does not consider the above problems due to the center hole of a magnetic recording media.
U.S. Pat. No. 5,853,962 discloses a method and apparatus for removing photoresist and redeposited materials in a semiconductor process using liquid carbon dioxide snow. However, the apparatus disclosed in U.S. Pat. No. 5,853,962, which is generally called Eco-Snow, is used in the semiconductor manufacturing process, and use of the apparatus for the magnetic recording media is not considered in the patent. Therefore, the problems due to the center hole cannot be solved with the apparatus.